✨ Electrical Wiring Regulations
2420
THE NEW ZEALAND GAZETTE.
[No. 48
TABLE V.—IMPREGNATED-PAPER AND LEAD-COVERED CABLES: CURRENT CARRYING CAPACITY (SUBJECT TO VOLTAGE-DROP) AND CORRESPONDING FALL IN PRESSURE.
| Nominal Area of Conductor. | Number and Diameter (In.) of Wires comprising Conductor. | Single Cables run in Pairs. | Concentric or Twin Cable. | Three-core Cable. | Approximate Total Length in Circuit (Lead and Return) for 1-volt Drop.* |
|---|---|---|---|---|---|
| 1. | 2. | 3. | 4. | 5. | 6. |
| Sq. in. | Amps. | Amps. | Amps. | Ft. | |
| 0·001 | 1/·036 | 4·1 | 3·5 | — | 30 |
| 0·0015 | 1/·044 | 6·1 | 5·2 | — | 30 |
| 0·002 | 3/·029 | 7·8 | 6·7 | — | 30 |
| 0·003 | 3/·036 | 12·0 | 10·3 | — | 29 |
| 0·003 | 1/·064 | 12·9 | 11·1 | — | 29 |
| 0·0045 | 7/·029 | 18·2 | 15·7 | 13·6 | 28 |
| 0·007 | 7/·036 | 28·0 | 24·0 | 21·0 | 27 |
| 0·01 | 7/·044 | 42·0 | 36·0 | 31·0 | 27 |
| 0·0145 | 7/·052 | 57·0 | 49·0 | 43·0 | 28 |
| 0·0225 | 7/·064 | 75·0 | 65·0 | 56·0 | 32 |
| 0·03 | 19/·044 | 87·0 | 76·0 | 66·0 | 35 |
| 0·04 | 19/·052 | 104·0 | 89·0 | 76·0 | 41 |
| 0·06 | 19/·064 | 135·0 | 116·0 | 97·0 | 48 |
| 0·075 | 19/·072 | 157·0 | 135·0 | 111·0 | 52 |
| 0·1 | 19/·083 | 191·0 | 162·0 | 134·0 | 57 |
| 0·12 | 37/·064 | 210·0 | 177·0 | 146·0 | 60 |
| 0·15 | 37/·072 | 246·0 | 204·0 | 170·0 | 65 |
| 0·2 | 37/·083 | 296·0 | 240·0 | 203·0 | 72 |
| 0·25 | 37/·093 | 343·0 | 265·0 | 233·0 | 78 |
| 0·3 | 37/·103 | 385·0 | 302·0 | 258·0 | 85 |
| 0·4 | 61/·093 | 464·0 | 354·0 | — | 95 |
| 0·5 | 61/·103 | 540·0 | 405·0 | — | 100 |
| 0·6 | 91/·093 | 624·0 | — | — | 105 |
| 0·75 | 91/·103 | 738·0 | — | — | 109 |
| 0·85 | 127/·093 | 815·0 | — | — | 116 |
| 1·0 | 127/·103 | 932·0 | — | — | 121 |
- With maximum permissible current (Col. 3).
The figures given in Table V apply to single cables run in pairs and to concentric, twin, and three-core cables run singly.
The maximum permissible currents (subject to voltage drop) for the various sizes of conductors up to 1 square inch in cross-sectional area are shown in columns 3, 4, and 5 of the table, which allows for a rise in temperature of 50 degrees F. for impregnated-paper cables. For sizes below 0·017 square inch the table is based on a current density of 4,000 amperes per square inch.
The table refers to situations where the temperature of the air does not exceed 80° F., and thus the normal maximum running temperature is 130° F. Impregnated-paper lead-covered cables for pressures not exceeding 660 volts should not be allowed to attain a permanent temperature higher than 176° F., and the figures therefore allow of a margin of 46 degrees F.
Where the temperature of the air exceeds 80° F., the permissible current should be reduced so that the maximum temperature of the impregnated-paper lead-covered cables does not exceed the figures given above.
The further limitation of the size of conductor by the permissible drop in voltage is dealt with in Regulation 80 (a).
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VUW Te Waharoa —
NZ Gazette 1927, No 48
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NZ Gazette 1927, No 48
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Electrical Wiring Regulations, 1927
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🏗️ Infrastructure & Public Works11 July 1927
Regulations, Electrical Wiring, Safety, Compliance, Conductors, Cables, Current-carrying Capacity, Insulation Resistance, Tables